9517

• UCREFRP Catalog Number: 9517
• Author: Granath, W. O., J. C. Lewis and G. W. Esch
• Title: An Ultrastructural Examination of the Scolex and Tegument of Bothriocephalus acheilognathi ‎(Cestoda
• USFW Year: 1983
• USFW - Doc Type: Pseudophyllidea)‎
• Copyright Material: YES

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VOL. 102, NO, 3, JULY 1983

247

(1980) made no mention of their distribution on E. salvelini, Tedesco & Cog-
gins (1980) speculated that tumuli may serve in eccrine secretion. However,
the functional significance of tumuli has not been elucidated, so it is difficult
to explain the distribution of these structures along the strobila.
The outer portion of the tegument of B. acheilognathi was composed of a
dense layer of microtriches, and while their morphology is somewhat differ-
ent between the scolex and the proglottids, each area possesses microtriches
of a single form. Scolex microtriches are longer and thinner than those on the
strobila. This apparent dimorphism, however, is not consistent for all cestode
species. For example, Thompson et aI. (1980) observed morphologic and size
differences among microtriches on the strobila and scolex, as well as differ-
ences within the same region of Proteocephalus tidswelli, Several investi-
gators have reported on the distribution of two types of microtriches found
on Mesocestoides corti (Hess, 1981; Hess & Guggenheim, 1977; Voge et aI.,
1979). Both filamentous and blade-like microtriches occur behind the suckers;
only filamentous forms are found at the posterior end of the strobila. Berger
& Mettrick (1971) reported that Hymenolepis diminuta has two morpholog-
ically distinct types of microtriches on the mature and gravid segments. Sim-
ilar patterns of microthrix distribution occur on H. nana and H, microstoma,
although the direction in which these structures bend varies among the three
species.
Microtriches within the bothria of B. acheilognathi are somewhat more
slender in appearance than microtriches on the adjacent outer tegument. An-
dersen (1975) also noted a similar appearance of the microtriches within the
bothria of Diphyllobothrium dendriticum, D. ditremum, and D, latum, but
the functional significance of these slender structures is not known,
Sensory cilia (sensilla) are spaced between microtriches of the strobila.
These structures were observed only in the tegument of proglottids and were
not seen within the scolex tegument. This observation is in contrast to that
of Jones (1975), who found sensory cilia in the tegument of the scolex of
Bothriocephalus scorpii but not on the strobila.
Webb & Davey (1974) conducted a thorough ultrastructural study of sensory
receptors in a cestode species. These investigators described two different
types of sensory structures from Hymenolepis microstoma. The sensory cilia
found in the tegument of the strobila of B. acheilognathi most closely resem-
ble the sensilla described from the scolex of H. microstoma, Both are char-
acte),"ized by a rather long cilium and the absence of ciliary rootlets. There
are two electron-dense collars within the dendritic bulb of the sensilla of H.
microstoma, but only one such collar is present in the bulb of B, acheilo-
gnathi. Moreover, sensilla of B, acheilognathi possess microtubules and a
few electron-lucent vesicles, Sensory bulbs of H. microstoma are packed with
such vesicles; microtubules were not discernible. The dendritic bulb of Rail-
lietina cesticillus possesses both electron-lucent vesicles and microtubules
(Blitz & Smyth, 1973),
Electron-dense collars appear to be a common feature of the sensilla of